Funding for a competitive renewal of the Program Project Grant that supports this research (AG16765, Dr. John H. Morrison, PD) was successfully secured during the current reporting period. Other project activities focused predominantly on the continuation and completion of ongoing long-term investigations examining the cognitive effects of several hormone treatment regimens in aged, ovariectormized rhesus monkeys. Those experiments, involving over 2 years of extensive neuropsychological assessment in each subject, are nearing completion. Continuing effort has also been directed at documenting the morphological effects of estrogen deficiency and treatment, and providing a window on the functional significance of observed effects, all results are evaluated in relation to the cognitive influence of hormone manipulation assessed in the same subjects. As detailed in a number of primary reports and reviews published during the current reporting period, the emerging results are consistent with the view that selective features of synaptic morphology and organization in the hippocampus and prefrontal cortex are sensitive to ovarian hormone regulation in the aged monkey brain, specifically in relation to the cognitive outcome of aging (e.g., Hara et al., 2011;Dumitriu et al., 2010;Wang et al., 2010).